A large helical antenna is an effective means to transmit and receive low frequency, radio frequency (RF) signals from a satellite. Generally, helix antennas with higher gains and greater directivity are accomplished by increasing the number of turns of the helix, which results in an increased antenna length. A gain of an antenna can also be enhanced with a cavity at the base of an antenna. This cavity can also reduce Passive Intermodulation (PIM) products. A compromise between the cavity geometry and the antenna length typically limits or dictates the dimensions of an antenna when the antenna is part of a spacecraft payload because of the desire for an efficient launch configuration. Achieving these antenna dimensions can often adversely limit antenna performance.
The size and geometry of the fairing of the launch vehicle limits the size and shape of antennas and spacecrafts. Antennas with high gain, like helical antennas with large numbers of turns, become more difficult to incorporate with spacecrafts and launch vehicles because of the size and length. Helices with larger reflector cavities need large amounts of cargo area of a launch vehicle. Further, long antennas have to be stabilized with complex and heavy restraining structures, which reduces the amount of payload that can be included in a launch vehicle or increases the cost do to additional power needed to get the payload to orbit.